1. Field of the Invention
The present invention relates to a design aid apparatus and a design evaluation method for an electronic device, and in particular to a design aid apparatus and a design evaluation method relating to electromagnetic wave radiation properties of an electronic device such as a printer or a fax machine.
2. Description of the Related Art
In recent electric and electronic devices, the technological difficulty of EMC (Electromagnetic Compatibility) design, which prevents generation of unnecessary electromagnetic wave noise and ensures resistance to external noise, has been increasing as sources of electromagnetic waves have increased with the digitalization and increased speed of electronic circuits and as external noise from cellular phones and the like has increased.
In order to efficiently carry out the EMC design of an apparatus, a design of the whole apparatus, especially a design of the grounding system, is important.
Conventionally, as a technique for effecting the design of the whole apparatus, numerical simulation techniques for calculating the electromagnetic field, such as the moment method described in, for example, Japanese Patent Application Laid-Open (JP-A) No. 7-302278, are known.
FIG. 20 shows a functional block diagram of a simulation apparatus using the conventional moment method. This simulation apparatus includes: a database 70 of three-dimensional CAD data, library data, or the like; an input unit 72 for converting CAD data of an electric circuit apparatus to be analyzed, which CAD data is input from the database 70, into structure information required to calculate an electromagnetic field strength, and then inputting the converted data into an electromagnetic field strength calculation unit 74; the electromagnetic field strength calculation unit 74 for calculating the electromagnetic field strength according to the input data; and an output unit 76 for outputting an obtained result.
In this simulation apparatus, structures of printed circuit boards, cables, leads, casings, and the like included in the electric circuit apparatus to be analyzed are input accurately, and consequently an electromagnetic field strength can be calculated with high precision.
In the above described conventional technique, in principle, simulation of an actual apparatus can be conducted with high precision. In actual practice, however, the electromagnetic field calculation unit needs a very long calculation time and a lot of memory space. Therefore, structures in the apparatus can be calculated only in considerably simplified models. This results in a problem that the conventional technique cannot be substantially utilized for the apparatus design.